According to a number of market research reports, printed electronic products have large market potential in the future, and the products are common in the continuous miniaturization of their volumes. To satisfy the design requirements for lighter, smaller, or thinner products, the size of each part in the products is strictly restricted. For instance, the line width of conductive wire used in the printed electronic products is reduced from hundreds of nanometers to dozens of nanometers, which leads to a stalemate between manufacturing capabilities and costs. Due to the enhancement of functionality of electronic devices, wiring density has been continuously increased, and more space is thus required, which brings about the need for double-layer or multilayer printed circuit boards.
However, the existing multilayer printed circuit boards must be made by performing not only the printing process but also the lithographic process, so as to form conductive vias and conductive layers. The lithographic process inevitably raises three major issues: environmental pollution, low manufacturing yield, and high manufacturing costs. Specifically, chemicals are required in the process of forming the double-layer/multilayer printed circuit board, such as a chemical plating solution, an electroplating solution, photoresist, a developer, and an etching solution, which often results in significant energy consumption and severe pollution. Besides, in the lithographic process, fine conductive lines are often formed by a metal etching technology. Thereby, undercuts may be generated at the bottom of the fine conductive lines during etching, the section of the fine conductive lines is shaped as an inverted trapezoid, and the yield of the resultant products is reduced. Moreover, in through-via technology, a polyimide (PI) substrate is often used, and therefore the PI substrate should be coated with a black glue (carbon glue), so as to be used as a conductive substrate. Last but not least, the existing electronic products are often characterized by reduced price, and thus the high manufacturing costs of the lithographic process are unaffordable.
From another perspective, the integration of the printing process and the lithographic process is still immature. For example, after the printing process is performed, the product obtained may contain a polymer material or other mixtures, which is likely to affect the performance of the equipment employed for performing the lithographic process; in addition, the difficulty in matching the polymer material with the photoresist cannot be easily overcome.